Title: Reliance on Habits at the Expense of Goal-Directed Control Following

Online Resource 2

Title: Reliance on Habits at the expense of Goal-Directed Control following

Dopamine Precursor Depletion

Authors: Sanne de Wit1,2, Holly R. Standing1,3, Elise E. DeVito1,3,4, Oliver J. Robinson1,3,5, K. Richard Ridderinkhof 2, Trevor W. Robbins1,6, Barbara J. Sahakian1,3

Affiliations:

1 Behavioral and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK

2 Amsterdam Center for the Study of Adaptive Control in Brain and Behavior (Acacia), Department of Developmental Psychology, University of Amsterdam, and Cognitive Science Center Amsterdam, University of Amsterdam, The Netherlands

3 Department of Psychiatry, University of Cambridge, Addenbrooke’s Hospital, Cambridge, UK

4 Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA

5 Section on Neuroimaging in Mood and Anxiety Disorders, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA

6 Department of Experimental Psychology, University of Cambridge, UK

Corresponding author:

Sanne de Wit ()

RT analysis of instrumental learning. The congruence effect was not due to a speed-accuracy tradeoff. Analysis of the RTs revealed a significant effect of discrimination (F(2,48) = 8.04, MSE = .054, p = .001), but pairwise comparisons established that this reflected relatively fast responding on congruent relative to incongruent (p = .005), and standard trials (p < .05). A significant main effect of block reflects the visible speeding of responding in the course of training (F(5,120) = 35.42, MSE = .130, p < .0005). Finally, APTD did not affect the overall speed of responding (F < 1).

RT analysis of outcome-devaluation test. Analysis of the RTs on test trials did not yield an effect of APTD (F(1,24) = 2.10, MSE = 5.261), nor an APTD*Discrimination interaction (F(2,48) = 1.92, MSE = 2.037). There was a marginally significant effect of discrimination type (F(2,48) = 3.00, MSE = 2.037, p = .07), but pairwise comparisons between the three discriminations did not yield any significant effects.